* {
  margin: 0;
  padding: 0;
}

body {
  height: 100vh;
}

header {
  display: block;
  margin: 0 auto;
  width: 100%;
  text-align: center;
}
header h1 {
  font-family: Arial;
  font-size: 40px;
  font-weight: bold;
}

header #newgamebutton {
  display: block;
  margin: 10px auto;
  padding: 10px;

  width: 100px;
  background-color: #8f7a66;

  font-family: Arial;
  color: white;

  border-radius: 10px;
  text-decoration: none;
}

header #newgamebutton:hover {
  background-color: #9f8b77;
}

header p {
  font-family: Arial;
  font-size: 25px;
  margin: 10px auto;
}

.grid-wrapper {
  margin: 10px auto;
  width: 92%;
  max-width: 500px;
  box-sizing: border-box;
}

#grid-container {
  -moz-user-select: none;
  /*火狐*/
  -webkit-user-select: none;
  /*webkit浏览器*/
  -ms-user-select: none;
  /*IE10*/
  -khtml-user-select: none;
  /*早期浏览器*/
  position: relative;

  width: 100%;
  height: 0;
  padding-bottom: 100%;

  background-color: #bbada0;
  border-radius: 10px;
}

.grid-cell {
  position: absolute;
  top: 0;
  left: 0;

  width: 20%;
  height: 0;
  padding-bottom: 20%;

  background-color: #ccc0b3;
  border-radius: 6px;
}

.number-cell {
  position: absolute;
  border-radius: 6px;

  font-family: Arial;
  font-weight: bold;
  font-size: 60px;
  line-height: 100px;
  text-align: center;
}
